Turbulator for heat exchanger

ABSTRACT

The efficiency of dimple-type turbulators located on roughly parallel walls defining a flow channel within a heat exchanger is increased by providing protuberances on the dimples themselves which enhance turbulence, and thus, increase the rate of heat exchange.

FIELD OF THE INVENTION

This invention relates to heat exchangers, and more particularly toimproved turbulators for heat exchangers.

BACKGROUND OF THE INVENTION

For many years, various types of turbulators have been employed in theflow channels for one or more heat exchange fluids in a heat exchanger.The turbulators induce turbulence in the flow of the heat exchange fluidthrough the channel and as is well known, the resulting increasedturbulence increases the heat exchange coefficient, which, in turn,increases the rate of heat transfer.

Turbulators come in many shapes and forms. In some cases, theturbulators are manufactured as elements separate from otherconstituents of the heat exchanger and are placed in a fluid flowchannel at the time of assembly of the heat exchanger with which theyare to be used. In other cases, turbulators are formed in the walls thatdefine a flow channel. This type of turbulator is frequently found inso-called plate heat exchangers, drawn cup heat exchangers, and in heatexchangers utilizing so-called flattened tubes. In each of these typesof heat exchangers, two or more generally parallel walls of high thermalconductivity, along with other constituents, define one or morechannels. Dimple-like turbulator structures are formed in one or both ofthe walls. In some cases, where the dimples are formed in only one wall,they will extend entirely across the channel to contact and typically bebonded to the opposite wall to improve the strength of the heatexchanger.

In some cases, dimples will be formed in both walls and extend acrossthe flow channel to be bonded to the opposite wall, again to providestrength. In still other cases, the dimples will be aligned with eachother and formed in both walls in which case the dimples extend onlyhalf-way across the flow channel and then are bonded to one another,again to provide strength to the heat exchanger.

A typical plate heat exchanger having dimples which serve as turbulatorsformed in only one wall of the flow channel is illustrated in Europeanpatent Publication EP 0 263 798 B1. An example of dimples formed on bothwalls and extending partway across the flow channel to be bonded t oneanother is illustrated, for example, in European patent Publication EP 0418 227 B1.

As mentioned in the '798 European patent publication, and as mentionedabove, it is common to provide turbulator plates in various flowchannels. The plates can be formed with a significant variety ofstructure that can be adapted to the particular heat exchangerequirements. However, from a manufacturing standpoint, the provision ofseparate turbulators is not the preferred choice because separate partsare involved that must be produced and inserted into the flow channels,thus complicating production and assembly.

Another restriction that hampers the use of separate turbulators is thatin many applications, a great degree of cleanliness of the flow channelsis required and residues used to bond the separate turbulators in placecan have deleterious effects on the entire system.

Thus, there is a real need for improved turbulator configurations wherethe turbulators are integrally formed with a wall or walls of a heatexchanger flow channel to avoid the problems associated with the use ofseparate turbulators and yet provide enhanced performance andadaptability to different heat exchange requirements that is morereadily achievable with separate turbulators.

SUMMARY OF THE INVENTION

The principal object of the invention is to provide a new and improvedturbulator structure for use in the flow channels of heat exchangers.More particularly, it is an object of the invention to provide a new andimproved turbulator that is integrally formed with the walls defining aflow channel in a heat exchanger.

An exemplary embodiment of the invention achieves the foregoing objectsin a heat exchanger having at least one flow channel for a heat exchangefluid defined by spaced, generally parallel walls between which the heatexchange fluid flows. A plurality of dimples are formed in at least oneof the walls to extend therefrom toward the other wall to be securedthereto or to another dimple extending from the other wall toward theone wall. The dimples, as is conventional, act as turbulators to induceturbulence in the heat exchange fluid as it flows between the generallyparallel walls. The invention specifically contemplates the provision ofprotrusions on the sides of the dimples that extend into the flowchannel or channels to increase the inducement of turbulence in the heatexchange fluid as it flows between the parallel walls and around thedimples.

In one embodiment, the walls are aluminum sheets and the dimples and theprotrusions are formed by a metal-forming die.

The invention contemplates that the dimples have bases integral with atleast one of the walls and opposite flat tops bonded to the other of thewalls or to the flat top of another of the dimples.

In one embodiment of the invention, the protrusions on the dimples arelocated between the base and flat top of the corresponding dimple.

In a preferred embodiment, the protrusions are ribs that extend from thebase to the flat top of the dimples.

In one embodiment, each dimple has a plurality of the ribs spaced fromone another about the periphery of the dimple.

A preferred embodiment contemplates that the ribs on each dimple aregenerally radially oriented. In a highly preferred embodiment, asmentioned previously, the dimples are die-formed in at least one of thewalls and the protrusions are integral with the sheet of which the wallis formed and die-formed in the dimples.

Other objects and advantages will become apparent from the followingspecification taken in connection with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is comprised of FIG. 1 a and FIG. 1 b and illustrates fragmentarycross sections of the turbulence inducing protrusions of the invention.FIG. 1 a and FIG. 1 b are representative cross sections takenapproximately along the line 1-1 in FIG. 2;

FIG. 2 is a fragmentary section taken approximately along the line 2-2in FIG. 3 or 4;

FIG. 3 is a plan view of a turbulator dimple with enhanced turbulatinginducing protrusions made according to the invention according to oneembodiment thereof;

FIG. 4 is a view similar to FIG. 3 but of a modified embodiment of aturbulence-inducing structure made according to the invention;

FIG. 5 illustrates flow channels employing turbulators according to theinvention in one form of a heat exchanger;

FIG. 6 is a fragmentary view showing still another example ofturbulators made according to the invention; and

FIG. 7 is a fragmentary, perspective view of a heat exchanger plateembodying turbulators made according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In considering the invention, it must be kept in mind that same is notlimited to any one specific type of heat exchanger. While it will mostoften be used in plate heat exchangers, drawn cup heat exchangers, orheat exchangers employing flattened tubes, those skilled in the art willreadily appreciate that the same is susceptible to use in any sort ofheat exchanger wherein flow channels are defined by two, generallyparallel walls in which turbulating dimples can be formed. Hence, norestriction to any particular type of heat exchanger is intended exceptinsofar as expressly stated in the appended claims.

With the foregoing in mind, reference is made to FIG. 7, which shows afragmentary perspective view of one type of heat exchanger,specifically, a housingless plate type heat exchanger with which theinvention can be used. Specifically, one plate used in the formation ofsuch a heat exchanger is illustrated and includes a base or wall section10 surrounding by a somewhat trapezoidally shaped flange 12. At thecorners, ports 14, 16, for two different heat exchange fluids areillustrated and the manner in which such ports 14, 16 are connected tolike ports in other plates that are generally identical in the overallconfiguration that is shown in FIG. 7 is well known and forms no part ofthe present invention.

Projecting upwardly from the wall 10 is a pattern of a plurality ofdimple-like turbulators 18 to be described in greater detailhereinafter. The pattern can take on any of a plurality of differentforms depending upon the heat exchange requirements of the heatexchanger, the type of flow, i.e., cross current, counter current, orconcurrent, etc., the overall resistance of the flow path within theheat exchanger, etc.

As is well known, the plates shown in FIG. 7 are frequently stacked asillustrated in FIG. 5 to form adjacent flow channels and as aconsequence, the wall 10 may be provided with downwardly directeddimples 20 at various locations and in a desired pattern to provided forturbulation in an adjacent flow channel.

Referring to FIG. 5, it is seen that a second plate 22 also providedwith a peripheral flange 24 substantially identical with the flange 12is nested within the flange 12 and abutted to flat tops 26 of theturbulators 18. Typically, the plates 10 and 22 are formed of aluminum,although other highly heat-conductive metals could be used as well.Braze alloy (not shown) is located at the interface of the flanges 12,24 and the point of contact between the flat tops 26 of the dimples 18and the plate 22 so that a brazing operation will bond all of thecomponents together. A fluid-tight seal is thus provided between theflanges 12 and 24 making for a housingless heat exchanger while thedimples 18 are brazed to the adjacent plate 22 to provide strength. Thenet result is that connected flow channels 28 are formed about thedimples 18.

FIG. 6 illustrates a different configuration that may be employed. Inthis case, both the plate 22 and the plate 10 are provided with thedimples 18, with dimples extending in opposite directions towards eachother and with the plates 10 and 22 bonded together at points ofabutment.

As can be seen in both FIGS. 5 and 6, the dimples 18 are provided withprotrusions 30 that are made according to the invention, and will now bedescribed. Referring to FIG. 3, the flat top of each dimple 26 isillustrated and it will be seen that the flat top is connected by agenerally frustoconical sidewall 32 to a base 34 which is, in reality,one or the other or both of the plates 10, 22. That is to say, the base32 is integral with the plates and the frustoconical sidewall and top 26integral with the plates 10 and 22 as well. The protuberances 30 areformed in the sidewall 32 and extend from the base 34 to the flat top 26at radially spaced locations. The protuberances, in the embodimentillustrated in FIG. 3, are in the form of ribs which extend generallyradially from the center of the flat top 26.

FIG. 4 shows a somewhat similar configuration but rather than having afrustoconical sidewall, the same is an oblong sidewall 36 that decreasesin dimension as one moves from the base 34 to the flat top 26. Again, aplurality of ribs are on the protuberances 30, and the same aregenerally radially extending from the top 26 to the base 34.

FIGS. 1 a, 1 b, and FIG. 2 show the protuberances 30 in cross section.

FIGS. 1 a and 1 b show that the rib-like protuberances 30 may haverelatively sharp apexes as desired. It will also be appreciated thatwith the dimples 18 being die-formed from the plates 10, 22, that theprotuberances 30 can be simultaneously formed using a concave die of thedesired configuration operating against radially outer surface 40 ofeach dimple 18 as shown in FIG. 1 a and a convex die operating againstthe radially inner surface 42 of each dimple 18 as shown in FIG. 1 b.

It should be noted that the protuberances 30 need not be in the form ofribs as shown in FIGS. 2, 3, and 4. They will, however, be formed of anykind of an interruption or almost micro fine structure located on thewalls 32 or 36 at a location between the base 34 and the flat top 26 ofeach dimple.

It is also observed that with two heat exchange fluids flowing inopposite sides of a plate, as, for example, the plate 10 as shown inFIG. 7, that the down turned dimples 20 may have differentconfigurations and orientations from the upturned dimples 18 anddifferent protrusions 30 as well to achieve desired heat exchangecharacteristics. Similarly, it is possible to use the dimples with theprotuberances in only the flow channels handing one heat exchange fluidand not the other.

The presence of the protrusions greatly enhances the turbulating effectprovided the dimples like those shown at 18 or 20 but without theprotrusions 30 to achieve efficiencies more comparable to those achievedwith the use of separate turbulators without the attendant disadvantageof the use of separate parts requiring additional assembly and/orcontamination problems as a result of extensive bonding operations.

Typically, the protuberances 30 can be in the millimeter range, and withsuch a height, will enhance the bonding of the flat tops 26 to theplates 20, 22.

1. In a heat exchanger having at least one flow channel for a heatexchange fluid defined by spaced, generally parallel walls between whichthe heat exchange fluid flows and a plurality of dimples formed in atleast one of the walls to extend therefrom toward the other wall to besecured thereto or to another dimple extending from said other walltoward said one wall and wherein the dimples act as turbulators toinduce turbulence in the heat exchange fluid as it flows between thegenerally parallel walls, the improvement comprising protrusions onsides of said dimples extending into said flow channel(s) to increasethe inducement of turbulence in said heat exchange fluid as it flowsbetween said parallel walls and around said dimples.
 2. The heatexchanger of claim 1 wherein said walls are aluminum sheets and saiddimples and said protrusions are formed by a metal forming die.
 3. Theheat exchanger of claim 1 wherein said dimples have bases integral withat least one of said walls and opposite flat tops bonded to the other ofsaid walls or to the flat top of another of said dimples, and saidprotrusions are ribs extending from the base to the flat top of thedimples.
 4. The heat exchanger of claim 3 wherein each dimple has aplurality of said ribs spaced from one another about the periphery ofthe dimple.
 5. The heat exchanger of claim 4 wherein the ribs on eachdimple are generally radially oriented.
 6. The heat exchanger of claim 1wherein said dimples have bases integral with at least one of said wallsand opposite flat tops bonded to the other of said walls or to the flattop of another of said dimples, and said protrusions on said dimple arelocated between the base and flat top of the corresponding dimple. 7.The heat exchanger of claim 6 wherein there is at least one protrusionon a dimple which is in the form of a rib extending from the base of thedimple to the top thereof.
 8. The heat exchanger of claim 6 wherein saidwalls are formed of a thermally conductive metal and said dimples aredie-formed in at least one of said walls, said protrusion being integralwith said sheet and die-formed in said dimples.